docs: Add CLAUDE.md for Wild Central

Document the project overview, architecture, development commands,
environment variables, and the service registration API contract.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CLAUDE.md

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+# CLAUDE.md
+
+## Project Overview
+
+Wild Central is the networking and coordination platform for the Wild product family. It runs as a standalone service on a local network device (e.g., Raspberry Pi) and manages:
+
+- **DNS** (dnsmasq) — internal name resolution + optional DHCP
+- **Gateway** (HAProxy) — L4 SNI passthrough + L7 HTTP reverse proxy with TLS termination
+- **Firewall** (nftables) — host firewall rules
+- **VPN** (WireGuard) — remote access with peer management
+- **TLS** (certbot) — certificate provisioning via DNS-01
+- **Tunnels** (cloudflared) — outbound-only public exposure via Cloudflare
+- **DDNS** (Cloudflare) — A record + CNAME management
+- **Security** (CrowdSec) — intrusion detection
+- **NATS JetStream** — coordination bus for service registration, presence, and events
+- **Service Registration** — the contract API for Wild Cloud and Wild Works
+
+## Architecture
+
+Wild Central is a Go service that manages Linux networking daemons via config file generation and systemctl commands. It provides an HTTP API and an embedded NATS JetStream server.
+
+**Consumers:**
+- **Wild Cloud** — registers k8s instance domains for L4 SNI passthrough
+- **Wild Works** — registers services for L7 HTTP reverse proxy with TLS termination
+
+Both connect to Central's NATS (port 4222) or use the HTTP API (port 5055) to register services.
+
+## Development
+
+```bash
+make dev    # Run with live reloading (requires air)
+make build  # Build binary
+make test   # Run tests
+make check  # Lint + test
+```
+
+### Environment Variables
+
+- `WILD_CENTRAL_DATA_DIR` — Data directory (default: `/var/lib/wild-central`)
+- `WILD_CENTRAL_NATS_PORT` — NATS listen port (default: `4222`)
+- `WILD_CENTRAL_DNSMASQ_CONFIG_PATH` — dnsmasq config path
+- `WILD_CENTRAL_HAPROXY_CONFIG_PATH` — HAProxy config path
+- `WILD_CENTRAL_NFTABLES_RULES_PATH` — nftables rules path
+- `WILD_CENTRAL_VPN_CONFIG_PATH` — WireGuard config path
+- `WILD_CENTRAL_CORS_ORIGINS` — Allowed CORS origins
+- `WILD_CENTRAL_STATIC_DIR` — Web UI static files directory
+- `WILD_CENTRAL_VITE_URL` — Vite dev server URL for frontend proxying
+
+## Service Registration API
+
+The key abstraction. Services register with Central to get DNS, proxy, TLS, and public exposure.
+
+```
+POST   /api/v1/services              Register a service
+GET    /api/v1/services              List all services
+GET    /api/v1/services/{name}       Get service details
+PATCH  /api/v1/services/{name}       Update service
+DELETE /api/v1/services/{name}       Deregister service
+```
+
+### Service payload
+
+```json
+{
+  "name": "my-api",
+  "source": "wild-works",
+  "domain": "my-api.payne.io",
+  "backend": {
+    "address": "192.168.8.60:9001",
+    "type": "http",
+    "health": "/health"
+  },
+  "reach": "internal",
+  "tls": "terminate"
+}
+```
+
+### Backend types
+
+- `tcp-passthrough` — L4, SNI routing, backend handles TLS (Wild Cloud k8s)
+- `http` — L7, Central terminates TLS with wildcard cert (Wild Works services)
+- `static` — L7, static file serving (Wild Works frontends)
+
+### Reach levels
+
+- `off` — localhost only
+- `internal` — LAN-visible (DNS + proxy + TLS)
+- `public` — internet-visible (+ tunnel or direct exposure)